Thermally responsive device



Nov. 7, 1944. R. R. PITTMAN 2,362,398

THERMALLY RESPONSIVE DEVICE Filed Aug. 1, 1942 2 Sheets-Sheet 1 LOW MELTING I POINT MATERIAL 2 HIGH MELTING POINT MATERIAL INVENTOR NOV. 7, 1944. R PlTTMAN 2,362,398

THERMALLY RESPONSIVE DEVICE Filed Aug. 1, 1942 2 Sheets-Sheet 2 FIRST INDICATING AND NON-DISCONNECTING i SECOND INDICATING l 6 L] AND DISCONNECTING I NVENTOR Patented Nov. 7, 1944 THERMALLY RESPONSIVE DEVICE Ralph R. Pittman, Pine Bluff, Ark.

Application August 1, 1942, Serial No. 453,297

Claims.

This invention relates generally to devices the operation of which is dependent upon the attainment of a predetermined temperature by an associated body. More particularly, the present inventionis characterized by the fusible materials employed in the device, and the indication and switching construction which depends for operation upon the fusing of these materials.

Among the objects of the present invention is the provision of a temperature responsive device embodying indicating means and both indicating and switching means which functions in response to fusing of fusible material to first indicate attainment of a predetermined temperature and to subsequently concurrently indicate attainment; of a relatively higher predetermined temperature and actuate the switching means; and means for re-setting the device to the normal position when the fusible material embodied therein has frozen. Other objects will be in part obvious, and in part pointed out hereinafter.

The invention comprises certain of the elements, and combinations thereof, features of con. struction and arrangement of parts to be exemplified in the description to follow, and the scope of the invention will be indicated in the accompanying claims.

In the drawings: Fig. l is a side elevational view of the device, shown partly in section; Figs. 2, 3, 4, and 5 are respectively sections taken along the lines 22, 3-3, 4-4, and 5-5 of Fig. 1; Fig. 6 illustrates a method of application of the device. Similar reference characters indicate corresponding parts in the several figures of the drawings.

Referring to the drawings, particularly first to Figs. 1 to 5 inclusive, the upper chamber of conducting material IO is threadedly joined to the lower chamber I I, these members, along with the upper closure l2 and the lower closure I3 constituting a housing for mechanism of the device. A partition I9, which is shown integral with and within the upper chamber I0 and which extends upwardly from the floor thereof toward the closure I2, divides the lower portion of the chamber I0 into two concentric annular channels.

The inner retaining member I! extends downwardly into the inner channel, and the member Il may be formed integrally with the hollow shaft I5, the latter extending downwardly into the lower chamber II through a centrally located bearing 41. In somewhat similar manner, the outer and larger retaining member l6 extends coaxially downward into the outer channel, and the solid shaft I4 extends successively, from a point near the closure I2, downwardly through a, centrally positioned opening in the upper horizontal portion of the retaining member I6 and thence coaxially through the hollow shaft I5 to a point beyond the lower surface of the closure I3. The outer retaining member I6 is rigidly fastened to the upper chamber I0 by means of the normally frozen fusible material 20 within the outer annular channel, and similarly the inner retaining member I! is normally held in fixed position through its engagement with the fusible material 2| within the inner annular channel.

The semaphore 3B is rigidly secured to the extended lower end of the inner and solid shaft I4 by means of the set screw 39, and the drivin spring 31 arranged with its convolutions around the shaft I4 so as to continuously urge the latter member toward rotation in a clockwise direction when viewed from above. To normally restrain such movement, the pawl I 8 is interposed between the upper end of the solid shaft I4 and the horizontal portion of the retaining member I6, one end of the pawl I8 being rigidly secured to the shaft I4 and the other end arranged to engage one of the circumferentially spaced openings 23, as shown in Fig. 2. Upon fusing of the fusible material 20, the retaining member I6 is freed to rotate within the outer channel under the influence of the driving spring 31, the-retaining member It, the pawl I8, the shaft I4 and the semaphore 38 all moving together until stopped in the first indicating position.

To establish the first indicating position, the ratchet wheel 26, through which the shaft I4 coaxially extends, is provided with the circumfentially spaced openings 40. The pawl 22, one end of which is rigidly secured to the hollow shaft I5 and the other end of which is arranged to engage one of the openings 40, as shown in Fig. 4,

normally locks the ratchet wheel against rotary motion in a clockwise direction when viewed from above. The detent pin 25 is rigidly secured to the shaft I4 and extends outwardly therefrom withe in the circumferential slot 26 of the lower portion ergy stored in the spring 31 is expended or the movement otherwise impeded. These elements include the solid shaft I4, the pawl IS, the outer retaining member IS, the hollow shaft IS, the retaining ring ll, the pawl 22, the ratchet wheel 24, the pin 25 and the semaphore 38, the movement of these elements concurrently causing establishment of the second indicating position.

In certain applications it is desirable to disconnect a connected circuit the load of which is causing excess temperature rise of associated apparatus, and to accomplish this end, a pair of conducting contacts 29 and 30 are peripherally spaced and extend through the insulating wall of the lower chamber ll, being respectively held in place by the lock nuts 3| and 34, and provided with the terminal nuts 32 and 35 for connecting the extended conductors 33 and 36. A resilient bridging contact 27 is secured, by means of the screws 28, to the hub of the ratchet wheel 2 for movement therewith, and arranged to electrically connect the respective contacts until the ratchet wheel 2% moves from the normal position, and to disconnect these contacts in response to such movement.

The device is illustrated when applied to an electric transformer in Fig. 6. The transformer casing 42 contains the cooling liquid 45 and the winding 44, the latter being serially connected to a load circuit through the bushing 43, the resilient conducting support 33, the device 4|, and the extended conductors 36 and 46.

For such application, it is desirable that a first indication be initially provided when the casing 42 attains a predetermined temperature corresponding to the full thermal load on the transformer, and that, upon attainment of a relatively higher predetermined temperature corresponding to damaging or excess load, a second indication be provided concurrently with disconnection of the load causing the excessive temperature rise.

To illustrate, assume that the fusible material 20 which is in engagement with the outer retaining member 16 is such that its melting point is 50 degrees centigrade, and that the fusible material which is in engagement with the inner retaining member i! is such that its melting point is 65 degrees centigrade. Under such conditions, the first indication occurs when the fusible material 20 melts to free the outer retaining member i6 for movement, the semaphore moving in response from the normal position to the first indicating position, as shown in Fig. 5. If the temperature rise continues, the fusible material 2| subsequently melts, freeing the inner retaining member IT, in response to which occurrence the semaphore 38 moves from the first to the second indicating position and the movable contact 21 moves concurrently to the open circuit position to effect disconnection of the load circuit.

When both of the fusible materials are fused, the device will not latch in either the normal or first indicatin positions. If, however, the material 2 I, in the inner channel, is frozen, the solid shaft [4 may be moved counterclockwise in direction, viewed from above, as the pawl 22 ratchets along the openings 40 of the ratchet wheel 24, to establish the semaphore 38 in the first indicating position and to close the switch. In somewhat similar manner, the semaphore may be turned to and latched in the normal position following the freezing of the material 20, in the asoaaca ets along the openings 23 of the upper and outer retaining member ID.

The arrangement above described, and illustrated by Fig. 6, has certain advantages over previous organizations. Heretofore indicating and switching temperature responsive devices have been used to perform functions substantially identical to those accomplished by the construction described herein, but such organizations have in general employed devices submerged within the cooling liquid, requiring more complicated and expensive arrangements which are relatively inaccessible and not at all suitable for embodying in existing transformers. It will be apparent from the description herein that the external construction employed in the present invention makes possible ready combination of the protective arrangement with existing transformers which may or may not be in service.

In the foregoing description of my invention, specific examples have been used, but it will be understood that this has been done for illustrative rather than for limiting purposes.

I claim as my invention:

1. A temperature indicator comprising a hollow tubular chamber, a rotatable shaft extending coaxially into and journalled for rotary movement with respect to said chamber, a concentrically disposed partition within said chamber arranged to provide an annular channel extending around said shaft in coaxial relationship therewith, a retaining member extending into said annular channel, ratchet means connecting said retaining member to said shaft so as to cause movement therewith in response to rotation of said shaft in only one direction, means biasing said shaft toward rotary movement in said one direction, and a body of fusible material positioned within said annular channel in engagement with said retaining member and joining said retaining member to said partition when said fusible material is unfused, the arrangement being such that said retaining member is released for rotary movement with said shaft when said material fuses, and a. visible indicator secured to said shaft externally of said chamber.

2. A temperature indicator comprising a hollow tubular chamber, a concentrically disposed partition within said chamber arranged to provide an inner and an outer annular channel, said channels extending within said tubular chamber in concentric relationship to one another, inner and outer retaining members extending downwardly respectively into said inner end outer channels, a hollow rotatable shaft integral with the inner retaining member extending therefrom coaxially with respect to said container and to a point outside of said chamber, another rotatable sh'aft extending through said hollow shaft into said chamber, detent means carried by said another shaft arranged to engage said hollow shaft when a predetermined rotary movement of said another shaft occurs ratchet means connecting said outer retaining member to said another shaft so as to cause movement therewith in response to rotation of said shaft in only one direction, fusible materials differing as to melting point disposed respectively in said channels in engagement with said retaining members for normally fastening said members to said chamber, means biasing said another shaft toward rotation in said one direction for rotating said another shaft sequentially from the normal position to a first position and outer channel, and in so doing the pawl is ratch- II thence to a e o d osit on n re po se to the sequential fusing of said fusible materials, and a visible indicator movable with said shaft for respectively indicating the positions thereof.

3. A temperature indicator comprising a hollow tubular chamber, a concentrically disposed partition within saidv chamber arranged to provide inner and outer annular channels extending with' in said tubular chamber in concentric relationship one to the other, inner and outer retaining members extending downwardly respectively into said inner and outer channels, a rotatable shaft associated with said retaining members and movable sequentially from a normal position to a first indicating position and thence to a second indicating position, ratchet means connecting said outer retaining member to said shaft so as to cause movement therewith in response to rotation of said shaft in only one direction, and detent means operatively connecting said shaft to the inner retaining member following a predetermined movement of said shaft in said one direction, fusible materials differening as to melting point disposed respectively in said channels in engagement with and normally restraining movement of said retaining members when said fusible materials are unfused, and individually releasing each of said retaining members when the material with which it is engaged fuses, means responsive to the sequential fusing of said fusible materials for rotating said shaft sequentially from said normal position to said first position and thence to said second position, and a visible indicator movable with said shaft for respectively indimovable with the inner retaining member ex-- tending therefrom to a point outside of said chamber and along the longitudinal axis of the chamber, another rotatable shaft extending through said hollow shaft into said chamber, ratchet means connecting said outer retaining member to said another shaft so as to cause movement therewith in response to rotation of said shaft in only one direction, fusible materials differing as to melting point disposed respectively in said channels in engagement with and restraining movement of said retaining members when said fusible materials are unfused, resilient means urging said another shaft toward rotation in said one direction, detent means carried by said another shaft and engageable with said hollow shaft for establishing the position of said another shaft able in one direction from a normal position to a first indicating position and thence to a second indicating position, means urging said shaft for movement in said one direction, a first fusible material disposed within one of said channels, a first retainin member extending in said one of said channels in contact with said first fusible material, means connecting said shaft to said first retaining member to normally restrain the first movement of said shaft from the normal to the first indicating position when said first fusible material is frozen and for releasing said shaft to permit said first movement when said first fusible material fuses, a second-fusible material having a higher melting point than said first fusible material disposed within the other of said channels, a second retaining member extending into the last-named channel in contact with said second fusible material, means connecting said shaft to the second retaining member to restrain the second movement of said shaft from the first indicating position to the second indicating position when said second fusible material is frozen and for releasing said shaft to permit said second movement when said second fusible material fuses, ratchet means cooperating with said shaft to permit restoration of said shaft from either indicating position to the normal position when said materials are frozen, and a. semaphore movable with said shaft for respectively visibly indicating said positions.

RALPH R. PIT'IMAN. 

